COMPOSITION AND INTERFACIAL ACTIVITY OF HYDROPHOBIC SULFIDE-TYPE EXTRACTANTS

The composition and interfacial activity of dihexyl sulphide (Elf), dodecyl methyl sulphide (two samples from Elf and Penwalt) and n-dodecyl hydroxyethyl sulphide (Elf) which are commercially available sulphide-type extractants have been investigated. Recrystallized n-dodecyl hydroxyethyl sulphide was found to be of high purity (i.e. impurities, if any, are below the detection level of a gas chromatograph equipped with an efficient capillary column), whereas it was shown that all the other sulphides contained many components which were separated and, for most of them, indentified by a GC/MS technique. Recrystallized n-dodecyl hydroxyethyl sulphide starts to adsorb at the 2 M HCl/dodecane interface at concentrations (typically 10(-3) M) of about one order of magnitude lower than dodecyl methyl sulphide (Elf or Penwalt). Dihexyl sulphide exhibits a very weak interfacial activity and the observed decrease in the interfacial tension in the system containing about 0.4 M dihexyl sulphide cannot be attributed with certainty to its own interfacial activity.